1. Field of the Invention
This invention relates to electrolytic chlorine generators. More particularly, it relates to means for introducing a pH-reducing agent into an electrolytic chamber for dissolving mineral deposits from electrolytic cells.
2. Description of the Prior Art
Electrolytic chlorine generators include electrolytic cells having plates that are coated on one side or both sides, depending upon the type of cell, with a platinum group metal (PGM) such as ruthenium, or similar coating.
The operation of an electrolytic chlorine generator has the side effect of gradually increasing the pH level of a body of water undergoing such chlorination. If the pH is too high, it can adversely affect the water quality and the effectiveness of the chlorine generated by the generator. Accordingly, the pH level of a swimming pool, spa, fountain, well, or other body of water equipped with an electrolytic chlorine generator and a circulating pump must be lowered periodically.
A pool, spa, fountain, well owner, or the like is required to periodically perform a test of the water to determine its pH level, and to add muriatic acid or other suitable pH-reducing agent to reduce the level if it is too high. The acid has a pH of about 0.1 and thus is extremely dangerous to handle and causes severe burns if it contacts the skin, open wounds, or the eyes.
There is therefore a need for an improved method for adjusting the pH of water in circulating water systems equipped with an electrolytic chlorine generator.
Moreover, the electrolytic cells that generate the chlorine are subject to degradation due to the formation of mineral deposits, typically calcium, thereon. The mineral deposits must therefore be removed as needed.
One prior art technique for cleaning the cells requires manually removing them from the chlorination system and soaking them in acid. In a typical swimming pool system, such manual cleaning is required about every two weeks. Such manual cleaning is burdensome, risky, and has the disadvantage of using excessive amounts of acid. The electrolytic cell or block of plates is removed from the circulation line and soaked for approximately five (5) minutes in a bucket containing a diluted hydrochloric acid solution of about one (1) part acid to five (5) parts water.
The frequency of manual cleaning may be reduced to quarterly if the polarity of the electric charge transmitted to the electrolytic plates is periodically reversed. Chlorine is produced on the anode plate or the anode side of a bipolar cell. Thus, in an ideal electrolytic cell, a PGM is applied only to the anode plate or the anode side of a bipolar cell. The cathode plate, or the cathode side of a bipolar cell, is not coated because such plate or side is merely needed to complete the electrical circuit.
However, in a practical electrolytic cell, the cathode plate and the cathode side of plates in a bipolar cell must also be coated because the polarity of the anode and cathode must be reversed periodically to clean the plates. More particularly, a system that requires polarity reversal is typically operated half the time in one polarity and half the time in the opposite polarity. A system that does not rely on reverse-polarity operation would thus reduce the amount of PGM-coated plates by half.
Unfortunately, reversing polarity has detrimental effects on the electrolytic plates. A PGM coating holds up well during anode operation, but steadily deteriorates during cathode operation. Thus it is desirable to operate PGM-coated plates only on the anode side and the uncoated plates only on the cathode side. Reversal of polarity results in cathode operation of the PGM coated side. Accordingly, cleaning of deposits from the plates by reversing the polarity of the anode and cathode should be minimized if not completely avoided. However, most electrolytic chlorine generators rely on polarity reversal as the primary means of removing calcium deposits from the plates.
Moreover, polarity reversal causes the plates to repeatedly charge up, and such charging up wears out the PGM coating at a much faster rate than steady state operation.
More specifically, charging the plates causes the plates to absorb a minor shock that wears out the PGM coating. This shock can be minimized by a gradual discharging of the plates, followed by a gradual re-charging at an opposite polarity. This method of reversing polarity is called the “soft start” method and reduces but does not eliminate the wear on the plates. Thus it is beneficial to eliminate or to at least reduce the number of times that the system is subjected to a reverse polarity, and to use the soft start method when a polarity reversal is required.
However, even with routine reversal of polarity, the electrolytic cells will still collect calcium deposits over time. At least some of the calcium deposits will eventually flake off and foul the body of water. In a swimming pool or spa, this unsightly debris is eventually suctioned by a pool cleaner or pool drain into a pool filter where the calcium is collected.
A need therefore exists for a method that will clean calcium deposits from electrolytic plates before the calcium flakes off from the plates.
Hardened calcium deposits do not easily dissolve back onto the body of water so they remain on the filter until it is removed from the system and cleaned. The calcium content of the water thus drops over time and requires replenishment because a swimming pool having low-calcium water will aggressively attack various pool walls and equipment.
Thus there is a need for an electrolytic chlorine generator that cleans calcium deposits from electrolytic plates but which does not result in removal of calcium from the body of water, and which therefore does not require that calcium be added periodically to a body of water.
Electrolytic chlorinators operate best when the salt content of the main body of water is between 2800 to 5000 parts per million. This high salinity adversely affects some swimmers if the main body of water is a swimming pool. Such high salinity may disqualify an electrolytic chlorinator from use where the main body of water is a fountain because salt may leave white marks on fixtures after a fixture has been splashed and the splashed water has evaporated.
A need therefore exists for an electrolytic chlorinator that operates well in a low salt environment.
It is known that the salt content of the water may be reduced if the surface area of the PGM-coated plates in the electrolytic cell is exponentially increased and the plates are spaced closer together to compensate for the lower conductivity of the water. Unfortunately, plates that are spaced close to one another become fouled with mineral deposits at a substantially faster rate than more widely spaced plates. This effect may be countered to some extent by increasing the flow rate of water past the plates and by reversing the polarity of the plates on a more frequent basis. Since maintaining higher flow rates often requires increased energy and equipment expenditures and the increased use of polarity reversal wastes the PGM, most systems forego the closer plate spacing and continue to require high salinity.
Thus there is a need for an electrolytic chlorinator that operates well at lower salt levels without requiring a higher flow rate and without increasing the consumption of PGM.
A general need exists for an improved method for cleaning calcium and other mineral deposits from the electrolytic cells of an electrolytic chlorine generator. The improved method would not have a detrimental effect on the electrolytic plates and would eliminate the need for biweekly or quarterly manual cleaning of the cells.
The improved method would also eliminate or at least substantially reduce the need for cleaning the plates by subjecting them to polarity reversal. Such an improved method would thus lower the requisite number of PGM-coated plates.
Peristaltic pumps for infusing an acidic agent into the line as the circulation pump is operating are in common use in large commercial fountain and swimming pool installations. However, such pumps are expensive and are subject to wearing out. There are also systems for infusing chemicals into the lines that harness the suction created by the circulation pump to pull the chemicals into the pump. This method has the drawback of causing aggressive chemicals such as hydrochloric acid to attack the circulating pump, filters, heaters, and any other equipment that might be present in the system. Since the pump is the first piece on the slab, it is affected the most by such aggressive agents.
Thus there is a need for an infusing means that infuses aggressive chemicals downstream of the pump and other pieces of equipment that are not designed to resist aggressive chemicals.
There is also a need for an infusion system that eliminates the need for a pump that is dedicated to infusion.
However, in view of the prior art taken as a whole at the time the present invention was made, it was not obvious to those of ordinary skill how the identified needs could be fulfilled.